Jobsite Know-How

Easy Joist Blocking for Wood I-Joists

Jan. 16, 2019

Engineered I-joists can span long distances to make a flat and solid subfloor. Tying the joists together with blocking makes the floor even stronger and stiffer. So one of the last things that need to be done before sheathing the deck is to fill in with joist blocking. Here are three steps for joist blocking. Read on to learn how to install blocking between joints.

Making “Professional” Blocks 

To make the blocks, I cut sections of I-joist 1½ inches smaller than the space between the joists, then nail a scrap of ¾-inch subfloor material to each end of the block [1]. This creates two large nailing fins.

Calvin Cutts works from a ladder to install the blocks. After lining up each block with the tops of the floor joists, he nails it in place, top and bottom, on both sides [2].

The subfloor strips are about ½ inch shorter than the full height of the I-joist [3] so that the nailing fins will not stick above the tops of the joists and cause humps in the floor. 

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About the Author

David Joyce

David Joyce owns Synergy Construction in Lancaster, Mass. This article is adapted from a video at ProTradeCraft.com. Thanks to David and his crew for  allowing us to hang out at their jobsite.

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